#ifndef M_BUF_H
#define M_BUF_H
#include"util.hpp"
#include<vector>
namespace dhylog{
    #define DEFAULT_BUFFER_SIZE (100*1024*1024)
    #define THRESHOLD_BUFFER_SIZE (80*1024*1024)
    #define INCREMENNT_BUFFER_SIZE (10*1024*1024)
    class Buffer{
        public:
            Buffer():_buffer(DEFAULT_BUFFER_SIZE),_writer_idx(0),_reader_idx(0){}
            //向缓冲区写入数据
            void push(const char*data,size_t len)
            {
                //缓冲区剩余空间不够的情况：1.扩容
                //1.固定大小，则直接返回
                //if(len>writeAbleSize()) return;
                //2.动态控件，用于极限性能测试--扩容
                ensureEnoughSize(len);
                //1.将数据拷贝到缓冲区
                std::copy(data,data+len,&_buffer[_writer_idx]);
                //2.将当前写入位置向后偏移
                moveWriter(len);  
            }
            size_t writeAbleSize()
            {
                return (_buffer.size()-_writer_idx);
            }
            //返回可读数据得起始地址
            const char*begin()
            {
                return &_buffer[_reader_idx];
            }
            //返回可读数据的长度
            size_t readAbleSize()
            {
                return (_writer_idx-_reader_idx);
            }
            void moveReader(size_t len)
            {
                assert(len<=readAbleSize());
                _reader_idx+=len;
            }
            //重置读写位置，初始化缓冲区
            void reset()
            {
                _writer_idx=0;
                _reader_idx=0;
            }
            //对Buffer实现交换操作
            void swap(Buffer &buffer)
            {
                _buffer.swap(buffer._buffer);
                std::swap(_reader_idx,buffer._reader_idx);
                std::swap(_writer_idx,buffer._writer_idx);
            }
            //判断缓冲区是否为空
            bool empty()
            {{
                return (_reader_idx==_writer_idx);
            }}
        private:
            //对空间进行扩容
            void ensureEnoughSize(size_t len)
            {
                if(len<=writeAbleSize()) return ;
                size_t new_size=0;
                if(_buffer.size()<THRESHOLD_BUFFER_SIZE)
                {
                    new_size=_buffer.size()*2;
                }
                else 
                {
                    new_size=_buffer.size()+INCREMENNT_BUFFER_SIZE;
                }
                _buffer.resize(new_size);

            }
            //对读写指针进行向后偏移操作
            void moveWriter(size_t len)
            {
                assert((len+_writer_idx)<=_buffer.size());
                _writer_idx+=len;

            }
        private:
        std::vector<char> _buffer;
        size_t _reader_idx;//当前可读数据的指针--本质是下标
        size_t _writer_idx;//当前可写的指针
    };
}
#endif